Congo red


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Con·go red

(kong'gō red), [C.I. 22120]
An acid direct cotton dye, it is absorbed by amyloid and induces green fluorescence to amyloid in polarized light; used as a laboratory aid in the diagnosis of amyloidosis, as a histologic stain, and as an indicator (pH 3, blue-violet, to pH 5, red) in testing for free hydrochloric acid in gastric contents. See: Bennhold Congo red stain.

Congo red

n.
A brownish-red powder, C32H22N6Na2O6S2, used in medicine and as a dye, indicator, and biological stain.

Con·go red

(kong'gō red)
[CI 22120] An acid direct cotton dye, used as an indicator (pH 3.0, blue-violet, to pH 5.0, red) in testing for free hydrochloric acid in gastric contents; the dye is absorbed by amyloid and induces green fluorescence to amyloid in polarized light; used as a laboratory aid in the diagnosis of amyloidosis and as a histologic stain.

Congo red

a synthetic dye, a derivative of benzidine and naphthionic acid. It is used for differential staining of elastic fibers for microscopic examination. Amyloid is stained a light orange-red with Congo red and exhibits apple green birefringence under polarized light. Amyloid in cats stains poorly. Congo red undergoes a change in hue with acidity and thus can be used as an indicator of pH, turning red in the presence of alkalis (bases) and blue when exposed to acids.

Congo red test
a laboratory test used in the diagnosis of amyloidosis, based on measuring the amount of injected dye that is removed by amyloid in the tissues of the human patient. Not now commonly used.
References in periodicals archive ?
Congo Red is commonly used as an indicator of pH and in histological staining for amyloid.
This provides an advantage from the use of MMPS over other stains for MCC, such as GMS or Congo red, which do not stain talc, mixed silicate, or oxalate crystals.
The net positive surface potential of sorbent media decreases, resulting in a reduction the electrostatic attraction between the (sorbent) Congo red species and the (sorbate) adsorbent material surface (RH), with a consequent reduced sorption capacity which ultimately leads to decrease in percentage adsorption of Congo red dye [11].
The only entity that is Congo red positive is amyloidosis, clinching the diagnosis.
Li, Rapid hydrothermal synthesis of magnetic Co x Ni 1 A x Fe 2 O 4 nanoparticles and their application on removal of Congo red, Chem.
sup][6] The gold standard to identify amyloid deposition is Congo red staining with apple-green birefringence under cross-polarized light.
The mechanism of commercial dye flocculation is similar to that discussed for congo red.
However, nonamyloid light-chain deposits are Congo red negative.
Aliquots (3 mL) of each flask were withdrawn at different time intervals (1, 2, 3 and 4 days) and the optical density was measured at 618 nm for malachite green, 462 nm for methyl orange and 485 nm for Congo red.
2 The use of Congo red staining methods to diagnose CA and further subtyping with immunofixation, serum free light chains, and mass spectrometry help differentiate light chain amyloidosis (AL) from transthyretin amyloidosis (ATTR): the two most common types of CA.
3) Diagnosis is confirmed by tissue and immunohistochemical staining with Congo red dye and the presence of applegreen birefringence on polarized microscopy.
An extended panel of IHC was applied which showed positivity for osteonectin, vimentin and a Ki 67 index of about 40-50% (fig-3) and negativity for CD 99, SMA, Desmin, ER, PR and Congo red, thus giving a definitive diagnosis of ESOS.